Photosensitive control circuit with automatic rearming



April 14, 1964 P. GARNICK ETAL 3,129,360

PHOTOSENSITIVE CONTROL CIRCUIT WITH AUTOMATIC REARMING Filed April 11, 1960 2 Sheets-Sheet 1 C-P COMMON PHOTO-CELL v FIG.I

INVENTORS: Philip Gornlck Winfield H.Benner BY Leslie Gwynne 4 IMF/b. ATTORNEYS.

Aprll 14, 1964 p, GARNICK E 3,129,360

PHQTOSENSITIVE CONTROL CIRCUIT WITH AUTOMATIC REARMING Filed April 11, 1960 2 Sheets-Sheet 2 G 4 INVENTORS:

Phlllp Garnlck BY Winfield H.Benner Leslie G. Wynne MA MK ATTORNEYS United States Patent 3,129,360 PHOTOENSKTIVE C(ENTROL CIRQUIT WITH AUTQMATIC REARMING Phidip Garnich, Needham, Winfield H. Benner, South Braintree, and Lesiie G. Wynne, Westwood, Mass, assignors to Sigma Instruments, Inc, a corporation of Massachusetts Filed Apr. 11, 1960, Ser. No. 21,291 8 Claims. (Cl. 317-124) The invention is concerned particularly with devices for automatically turning on lights at night and turning them off during the day.

The invention provides improved control apparatus and circuits for circuit controlling devices responsive to sensing devices such as photosensitive cells. It is particularly applicable to the operation of sensitive relays with alternating current. Although a particular example of the invention is described herein, it is to be understood that the invention is applicable to other uses.

In circuits of the type mentioned above the photocell is connected to control the current to a relay to cause the lights to be turned on when the amount of light reaching the photocell decreases to a given value. When sufficient light reaches the photocell at a later time there is a current through the relay to cause it to be actuated and thereby turn off the lights.

A feature of the invention and one object thereof is the provision of means for preventing the lights from being turned on when the amount of light reaching the photocell diminishes and for enabling the circuit to restore itself to its normal condition when, say, during the next morning, suflicient light reaches the photocell to cause the relay to drop out.

Another object of the invention is to enable the apparatus to be reset to a normal condition at will after it has been set to prevent the turning on of the lights.

A further object of the invention is to provide a compact and efficient device for automatic control and manual supervisory control of the turning on and off of lights at predetermined times.

The invention will be fully understood and other objects and advantages thereof will become apparent in the following drawings in which:

PEG. 1 is a circuit diagram of one embodiment of the invention;

FIG. 2 is a front sectional view of the apparatus;

FIG. 3 is a sectional view taken on the line 3--3 of FIG. 2;

FIG. 4 is a rear view of the apparatus with a portion of the cover broken away; and

FIG. 5 is a detailed sectional view showing one of the push button switches.

Referring to FIG. 1, an alternating current supply line is adapted to be connected to the terminals and 11 and a suitable load such as lights to be controlled is adapted to be connected between terminals 11 and 12. A photocell 13, a winding 14 of relay A and a resistor 15 are connected between terminals 10 and 11. The winding 14 has an iron core 16 and is adapted to operate the normally closed relay contact 17. Between contact 17 and resistor 15 there is connected another resistor 18 forming a voltage divider with resistor 15. The winding 20 of relay B is connected across the current supply line, that is, between terminals 10 and 11, through manually controlled switches 21 and 22 and the normally closed contacts 17. Switches 21 and 22 are preferably momentary switches operated by push buttons 42 and 41, switch 21 being normally closed and switch 22 normally open. Relay B includes a pair of normally opened contacts 25 and a pair of normally closed contacts 24.

The operation of the circuit is as follows: when relay 3,1293% Patented Apr. 14, 1964 A is not energized contacts 17 are closed and current is supplied from terminal 10 through these contacts and normally closed contacts 24 and then to the load between terminals 11 and 12. Resistors 15 and 18 form a voltage divider so that the voltage across winding 14 and photocell 13 is less than the line voltage by a considerable amount. Generally, resistor 15 is made of somewhat smaller resistance than resistor 18. When sufficient light falls on photocell 13, that is during the daylight hours, Winding 14 will be energized and begin to close its armature and also open the normally closed contact 17 Since the impedance of the winding 14 increases as the armature begins to close, the current through this winding would tend to drop if the voltage across it remained constant and the alternating current would cause the relay to chatter. The opening of contacts 17, however, causes the potential at the point between winding 14 and the connection between resistors 15 and 18, to rise to the value of the potential of terminal 11 and thereby increase the current through winding 14 sufiiciently to overcome the tendency toward chattering.

If it is desired to turn off the lights during the dark hours, push button switch 22 may be momentarily closed. Relay winding 26) is then energized opening contacts 24 and closing contacts 25. Winding 20 then remains energized through the latter contacts. If, after operating switch 22, it is desired to restore the circuit to its normal condition, push button 42 marked on is pressed to open switch 21 causing Winding 20 to be de-energized and cotacts 25 to be reopened and contacts 24 reclosed. If off switch 22 has been closed and relay B is actuated, then, during the dark hours, when contacts 17 are closed, the load will not be energized because contacts 24 are open. When, later, the photocell is illuminated and relay A opens contacts 17, relay B will be de-energized thus closing contacts 24, opening contacts 25 and restoring the circuit to normal operation.

Referring now to FIGS. 2, 3 and 4, there is provided a housing 30 formed of a suitable insulating material and having trapezoidal sides 31 and 32 and a base 33. The sides are provided with slots 34 into which there is inserted a chassis 35. The housing includes a seat 36 for receiving a cord and plug set 37, 38 having three wires extending to the three terminals as shown in FIG. 1. On the front of the chassis there are mounted the photocell 13 and relays A and B. Push button switches 21 and 22 are located at the upper end of the chassis. These switches are similar except that in switch 21 contacts 37 and 38 are spring biased into engagement, while in switch 22 the contacts are spring biased out of engagement. The switches are provided with push buttons 41 and 42 and will be described in greater detail in connection wtih FIG. 5.

The sides 31 and 32 of the housing are provided with flanges 43 extending around to the sides and tops thereof and a perforated cover 45, preferably in the form of a metallic grill, is mounted on the flanges and encloses the housing. At the four corners the cover 45 is provided with lugs and nuts 46 for receiving screws 47 holding the cover on the housing. Over the heads of the screws 47 there are provided rubber feet 48. Resistor 18 and other elements of the circuit are preferably mounted on the back of chassis 35. Within the cover 45 and closely adjacent thereto on the sides and top thereof there is a clear, plastic dust cover 54 The plastic cover 50 is provided with holes 51 permitting the plungers 52 of the push buttons to extend therethrough but forming a support for the push buttons themselves. This feature has been found to be very expeditions in supporting the push buttons during assembly of the apparatus.

Referring particularly to FIG. 5, the switch 22 is shown as including the off push button 41 extending through an opening in cover 45 and provided with a flange 53 supported on the plastic cover 50 with its plunger 52 extending through the hole 51. of the plastic cover. The plunger 52 engages the movable contact dil which is urged upwardly by spring 54 andis held in a given position by a retaining spring 55. The other contact 39 of the switch is cut out so that it is normally removed from contact lli. Upon depressing push button 41 the plunger 52'presses contact 40 into engagement with contact 39 causing energization of' the winding 2'0 of relay B as previously described. The chassis 35 is provided with a seat 56 supporting the various elements of the switch.

While the invention finds particular utility in circuits controlled by a photo conductor and relays of the characters described, it is not limited to such use, but may be applied in connection with other control elements such as transducers, thermistors, varistors, and rheostats or any device which presents an output in the form of a varying resistance. Since various modifications and variations of the invention may be made without departing from the principlesthereof, it is not to be construed as limited except as defined in the following claims.

We claim:

1. A control circuit comprising-a pair of current supply terminals, a photo-conductor and an electromagnetic relay having a winding connected in series with the photoconductor between said terminals, a load, said relayhaving a pair of normally closed contacts connected in series with said load between said terminals, a second relay having a winding and a pair of normally open contacts both connected in series with said normally closed contacts between said terminms, said second relay having a pair of normally closed contacts connected in series with the load and the normally closed contacts of the first relay, whereby the load is disconnected when either relay is energized sufficiently, and a normally open manually operable switch connected in parallel with the normally open contacts of the second relay.

2. An alternating current control circuit comprising a pair of current supply terminals, a photo-conductor and anelectromagnetic relay having a winding connected in series with the photo-conductor between said terminals, a load, said relay having a pair of normally closed contacts connected in series with said load between said terminals, a second relay having a winding and a pair of normally open contacts connected in series with said normally closed contacts both between said terminals, said second relay having a pair of normally closed contacts connected in series with the load and the normally closed contacts of the first relay, whereby the load is disconnected when either relay is energized sufficiently, a-normally closed manually operable switch connected in series with the second relay winding, and a normally open manually operable switch connected in parallel with the normally open contacts of the second relay.

3; A control circuit according to claim 2, comprising a voltage divider connected from one terminal through the normally closed contacts of the first relay tothe other closed contacts of the first relay, whereby the load terminal is disconnected from the other terminals when either relay is energized sufiiciently, and a normally open manually operable switch connected in parallel with the normally open contacts of the second relay.

5. A control circuit comprising a pair of current supply terminals, a first circuit breaker, means connected 7 to said circuit breaker for operating the same in response to a predetermined condition, a load terminal, said circuit breaker having a pair of normally closed contacts connected in series between said load terminal and one of said current supply terminals, a second circuit breaker having a pair of normally open contacts connected in series with. said normally closed contacts between said current supply terminals, said second circuit breaker having a pair of normally closed contacts connected in series with the. load terminal and the normally closed contacts of the first circuit breaker, whereby the load is disconnected when'either circuit breaker is operated and manuallyv controllable means for actuating said second circuit breaker and for automatically restoring it to its unactuated condition in response to a predetermined light condition.

6. Control apparatus comprising a housing having a base and a pair' of opposite sides extending from the base, a rigid perforated cover having a front Wall and a rear wallinterconnected by a top wall extending round the sides and substantially closing said housing, said cover having an opening in its top wall, a manually operable switch means extending through said opening and having a flange below the cover extending beyond the opening, a transparent plastic dust shield inside said cover and adjacent the front, rear and top Walls thereof, the top wall of said shield being below said flange for supporting said manually operable switch means and having an opening through which said switch means extends, and a circuit in said housing'including a pair of relays, and aphotocell having its light sensitive side exposed to receive light entering through the cover and shield, said photocell actuating one said relay upon the occurrence of a predetermined light intensity, said switch means actuating the other said relay to form a bypass circuit for said one relay.

7. Apparatus according to claim 6, including a vertical chassis fastened to the sides. of the housing, said circuit being mounted on said chassis and including a switch contact on the upper edge of the chassis juxtaposed to said manually operable switch means so as to be operable thereby.

8. A photo-electric control device comprising current supply means having a pair of terminals, load means having a connection to one said terminal, first relay means connected between said terminals and first contact means terminal, said photo-conductor and first relay winding being connected from an intermediate point on said voltage divider to said other terminal.

4. A control circuit comprising a pair of current supply terminals, a relay having a winding, means connected controlled by saidfirst relay means to provide a connectionbetween said load and the other said terminal, light sensitive means connected between said terminals and to said first relay, to actuate said first relay and'first contact means upon the occurrence of predetermined light conditions, a second relay and second contact means connected between said terminalsito bypass said first relay means, manually operable switch means connected in serieswith said second relay to actuate said second relay and second contact to bypass saidfirst relay and permit said load to be disconnected from and reconnected to said other terminal.

References Cited in the file of this patent UNITED STATES PATENTS 2,331,475 Johnson Oct. 12, 1943 2,538,536 Ritchie et al. Jan. 16, 1951 2,697,803- Eadie et al. Dec. 21, 1954 

1. A CONTROL CIRCUIT COMPRISING A PAIR OF CURRENT SUPPLY TERMINALS, A PHOTO-CONDUCTOR AND AN ELECTROMAGNETIC RELAY HAVING A WINDING CONNECTED IN SERIES WITH THE PHOTOCONDUCTOR BETWEEN SAID TERMINALS, A LOAD, SAID RELAY HAVING A PAIR OF NORMALLY CLOSED CONTACTS CONNECTED IN SERIES WITH SAID LOAD BETWEEN SAID TERMINALS, A SECOND RELAY HAVING A WINDING AND A PAIR OF NORMALLY OPEN CONTACTS BOTH CONNECTED IN SERIES WITH SAID NORMALLY CLOSED CONTACTS BETWEEN SAID TERMINALS, SAID SECOND RELAY HAVING A PAIR OF NORMALLY CLOSED CONTACTS CONNECTED IN SERIES WITH THE LOAD AND THE NORMALLY CLOSED CONTACTS OF THE FIRST RELAY, WHEREBY THE LOAD IS DISCONNECTED WHEN EITHER RELAY IS ENERGIZED SUFFICIENTLY, AND A NORMALLY OPEN MANUALLY OPERABLE SWITCH CONNECTED IN PARALLEL WITH THE NORMALLY OPEN CONTACTS OF THE SECOND RELAY. 